Ink jet printers and plotters are well known. The print quality of these printers is dependent on the consistent, successful functioning of the ink jet print heads which are susceptible to clogging and failure over time. To overcome the problems with deterioration of ink jet print heads over time, it is necessary to periodically replace the print heads. Early solutions to this problem replaced only the print head, as shown, for example, in U.S. Pat. No. 4,074,284. More recently, disposable ink jet cartridges have been developed to solve this problem, as described, for example, in U.S. Pat. Nos. 4,500,895, 4,921,811 and 4,931,812.
Disposable ink jet cartridges of this type are designed to operate for a useful life such that the head elements will function a very high percentage of the time (e.g., 99% of the time) during the life of the disposable cartridge. To ensure that this demanding performance figure is maintained, conventional disposable ink jet cartridges have a predetermined amount of ink contained within the cartridge that is available to be dispensed through the print head. The maximum amount of ink that is contained in the disposable cartridge is a function of how much printing the print head elements can do before failing to function at the very high performance percentage. Once the predetermined amount of ink in the cartridge is used, the entire ink jet cartridge is discarded.
While the use of disposable cartridge has effectively guaranteed the print quality of ink jet printers at the failure rate dictated by the particular disposable cartridge, there are many print applications which could tolerate a higher failure rate in exchange for an extended period of operation of the ink jet print head. Unfortunately, when existing disposable ink jet cartridges run out of ink, the print head is still functioning adequately in the vast majority of cases. Discarding ink jet cartridges that still have adequately functioning print heads wastes resources. In addition, frequent replacement of ink jet cartridges is time and labor intensive for large print applications. Consequently, many users have resorted to refilling ink jet cartridges in order to prolong the useful life of the print heads.
Manually refilling ink jet cartridges can be a messy and potentially hazardous operation that requires significant mechanical skill. To manually refill an ink jet cartridge, a user must access the original ink supply container in the ink jet cartridge and pump, pour or otherwise force ink into that supply container. Accessing any of ink couplings exposes the user to the ink and the ink to contamination. In addition, the user may inadvertently introduce air bubbles into the system which affects the flow of the ink and its ability to provide crisp, even print.
One method of refilling ink jet cartridges involves the use of a mechanical system of valves and pumps as described in U.S. Pat. No. 4,680,696. In addition to the complexity and expense of such a mechanical refill system, mechanical mechanisms are more likely to require additional maintenance and are more prone to failure than systems with few or no moving parts. Endless refill systems of this type are also susceptible to bacteria growth due to the presence of liquids in the system over long period of time that may clog or contaminate the printer.
An alternative method of refilling an ink jet printer uses gravity as controlled by a three way valve to feed ink from an ink reservoir to an ink supply container as part of a single replaceable unit, as described, for example, in U.S. Pat. No. 4,959,667. Early versions of this type of single replaceable unit ink delivery system as shown, for example, in U.S. Pat. Nos. 4,714,937 and 4,885,595. This method may be useful when the print heads are printing vertically and the ink reservoir can be positioned behind the print heads and above the ink supply container. When the print heads are printing on a large horizontal surface, however, the print head performance would be diminished if the weight and volume of a large reservoir of ink would need to be supported above the print heads as they operate.
While the use of disposable ink jet cartridges has significantly increased the print quality of ink jet printers, this increase in print quality has come at the expense of a significant waste of resources in the form of empty ink jet cartridges that still have long periods of useable life remaining for the print heads. Existing techniques to refill ink jet printers suffer from numerous drawbacks. Consequently, a disposable ink jet cartridge refill system that was easy to install, held significant volumes of ink, contained few moving parts, minimized ink contamination and unwanted air in the ink delivery system and conserved resources would be greatly appreciated.